Thermostat



Nov. 19, 1940.

J. S. BAKER El AL THERMOSTAT Filed March 14, 1938 3 Sheets-Sheet 1 HHIHHhu Nov. 19, 1940.

J. 5. BAKER ETAL THERMOS TAT Filed March 14, 1938 3 Sheets-Sheet 2 NOV.19, 1940. BAKER ETAL 2,222,062

THERMOSTAT Filed March 14, 1938 3 Sheets-Sheet 3 Patented Nov. 19, 1940UNITED STATES PATENT OFFICE THERMOSTAT Application March 14, 1938,Serial No. 195,732

25 Claims.

This invention relates to thermostats and is more particularly directedto a snap action thermostat.

Thermostats of the type herein disclosed are 5 used largely in heatingsystems to control operation in accordance with ambient temperaturechanges in the space to be heated. They have been the subject ofconsiderable development.

1 Simple thermostats consisting of a contact memresponsive elementflutter when making and breaking contacts. This results in rapiddeterioration of the contacts. To overcome this I difficulty, magnetshave been employed. The use 15 of magnets in a thermostat is notsatisfactory.

They increase the cost and render it impossible to maintain accuratelythe calibration of the instrument, due to their strength changing withage. Furthermore, magnets collect particles of magnetic material whichprevent closing of the contacts. On the other hand, spring mountedcontacts have been used to secure a quick break or snap action of themovable contact without a fluttering movement. This type of device hasmet with much trouble thus far, largely due to construction and design.If a thermostat is not sturdily built and its parts are not designed andassembledtogadmit of easy and accurate calibration, and-b apable ofmaintaining its temperature setting, the device necessarily has littlepractical value. One of the most serious difliculties heretoforeexperienced has been the inability of the construction to withstandrough handling during shipment. Quick loss of factory storing it on thejob have resulted in numerous replacements and consequent losses to themanufacturers.

An object of this invention resides, therefore, in the provision of athermostat of the character described that is sturdy in construction,that may be easily assembled in the shop and readily calibrated tooperate at predetermined temperalture settings,- that will retain suchcalibration during shipping and resist reasonably rough handling, thatis exceedingly sensitive to temperature changes,- and, although providedwith a snap action element that may be actuated by a very lightpressure, will effect maximum contact pressure at the moment of thebreak and thereby efiect a quick and positive break between thecontacts.

A further object of the invention is to provide in a thermostat of thecharacter described, having the aforesaid characteristics, certain reherconnected to or operated by a thermo adjustment and the attendantdifliculties of refinements in construction and operation that increaseefficiency, sensitivity and reliability over a long period of time.

A still further object of the invention is to provide a constructionthat is sturdy and easily 5 and effectively calibrated to operate atpredetermined temperature settings with a high degree of sensitivity totemperature changes, the construction being simple and relativelyinexpensive for its sensitive and reliable performance.

Primarily, the purpose of the invention is to provide a snap actionthermostat of the character described that is practical and highlyuseful.

Specifically, a thermostatic element, preferably of bimetal and U-shape,is supported by a mounting that tends to urge the legs together in amanner giving a free-floating action but still urging one of the legs ina direction opposite to its direction of movement upon a temperaturechange to break the circuit. A bowed spring carrying a movable contactmounted upon said thermostatic leg is caused to remain under the tensionof its bowing, which tension is progressively increased by the movementof this leg upon being influenced by a temperature change until maximumpressure (contact) is obtained at the moment the contacts are broken bya snap action. A manually adjustable member acting to modify the actionof the mounting upon the thermostatic element is employed topredetermine the temperature settings at which the moyable contact willbe actuated by the thermostatic element to make or break the circuit. Inorder to calibrate the action of the various parts in their propercoordinating relation to operate to break or make contact at saidpredetermined temperature settings, means are provided that furthermodify the action of the manually adjustable member. The'parts arearranged to secure great sensitivity of movement in order that thethermostatic element will quickly respond to changes in temperature. Thestructure 'is easy to assemble and adjust, and will keep its adjustmentwithout difficulty.

A furtherobject of the invention is prefer- ,ably. to provide thebimetallic element with its member of greater expansibility on theoutside of the U so as to overcome any tendency of the bimetallicelement to lose its adjustment during shipment if required to besubjected to abnormally low temperatures.

Other objects and advantages of the invention will be apparent from thefollowing detailed ex- 56 planation when taken in connection with theaccompanying drawings which form a part hereof.

In the drawings:

Figure 1 is a view of the device with the front cover removed;

Fig. 2 is an elevation of one side of the device but with the cover incross section;

Fig. 2a is a detail elevational view of a portion of the cover;

Fig. 3 is a view similar to Fig. 2, but of the opposite side; 7

Fig. 4 is a front view of the base with the parts removed;

Fig. 5 is a section through the base taken on line 5-5 of Fig. 4, butwith one of the terminal contacts in position;

Fig. 6 is a detail view of the thermostatic element;

Fig. 7 is a side view of one leg of the thermostatic elementillustrating the bowed spring in side elevation;

Fig. 8 is a view of the bowed spring in its position when the movablecontact engages the cold contact;

Fig. 9 is a similar view but with the bowed spring in its oppositeposition with the movable contact engaging the hot contact;

Fig. 10 is an enlarged detail view illustrating the movable contact onthe bowed spring;

Fig. 11 is a detail view of the fixed stop member and stationary contactmember at one side of the thermostatic element;

Fig. 12 is a similar view of the fixed stop member and stationarycontact member at the opposite side;

Fig. 13 is a detail sectional view illustrating the position of themovable contact engaging the cold contact and the position of thebimetallic leg (carrying this movable contact) engaging the fixed stopmember that is in circuit with this cold contact; this relation of theparts being established by the action of the spring mounting of thebimetallic member urging its legs together;

Fig. 14 is a similar view illustrating the position of said parts aftersaid action of the spring mounting to urge the bimetallic legs togetherhas been modified by a manually adjustable member in order to set thedevice to make or break circuit at a predetermined temperature;

Fig. 15 is a similar view of these parts after the snap over action ofthe bowed spring, carrying the movable contact, has been effected by achange in position of the bimetallic element through a change intemperature:

Fig. 16 is a similar view of these parts after the bimetallic leg hasbeen moved to a position engaging the opposite fixed stop member by themanually adjustable member;

Fig. 17 is a similar view of these parts illustrating the bimetallic legmember after breaking contact with the fixed stop member and in aposition to be influenced by a predetermined temperature change toactuate movable contact bya snap action to the opposite stationarycontact member;

Fig. 181s an enlarged detail sectional view illustrating the calibratingmeans;

Fig. 19 is a top plan view of the thermostat showing the cover partly inelevation but with the base of the device in section to illustrate thewall mounting plate;

Fig. 20 is a rear elevation of the thermostat illustrating the wallmounting member attached;

and,

Fig. 21 is a face view of this mounting member when secured to the wall.

Referring more particularly to the drawings, it will be noted that thethermostat comprises a base I that may be molded preferably of insula-'tion material in any desired shape or form to carry the terminalconnections and operating parts. A cover 2 is fitted over the front faceand held by screws 3 extending from the vertical sides of the base.Cover 2 may be apertured at 4 on each side and in the bottom to permitfree circulation of air therethrough and may, if desired, carry athermometer 5. Front face 6 of housing 2 may be slotted at I to receivea pointer 8 at the tip of a manually adjustable member 9 for cooperatingwith calibration markings 3 along the upper edge of slot I.

To position the various terminals carried by base I, raised faces III,II and I2 may be molded upon the front face of base I. To facilitate theassembling of the terminals and their proper positioning upon base I,ribs or projections I3, I4 and I5 may be formed. Terminal screws I6 andII are adapted to be threaded into bushings I3 from the rear side toprovide connections for a twowire circuit. The device may be adapted toa three-wire circuit through the use of a terminal screw I8, illustratedin Figs. 4 and 20. The specific type of connection may be varied, butthere is illustrated in the specific form shown in the drawings abushing I9 that is internally threaded to receive screws I6, I1 and I3.Line connections may be made at the screw terminals I6, I1 and I3 fromthe rear face of base I. An L-bracket 20 is secured by bushing l9against rib I4. Proiecting leg 2I of bracket 20 is apertured to receivea bolt 22' that receives and fastens the lower end of a mounting spring22 to said bracket 20. The opposite end of mounting spring 22 is securedto one leg of a bimetallic member 23 of U- shape whereby the latter isprovided with a freefloating support, spring mounting 22 acting,however, to tilt both legs clockwise about bolt 22. Bolt 22' rides inslot 24 (Fig. 5) in the lower end of spring mounting 22 which providesan adjustable connection permitting vertical adjustment of springmounting 22, and, consequently, a similar adjustment ofthe bimetallicelement 23.

The opposite side of the circuit represented by terminal screw I 6continues by means of a strap 25 held at one end upon raised face II bybushing I3 and at the other end upon raised face I2 by a similarconnection. This connection also secures an L-bracket 26 upon raisedface I2 against rib I 5. A preheating element 21 is secured by bolt 28to bracket 26 and lies adjacent one of the two legs 23 and 30 ofbimetallic member 23 so as to influence the action of leg 29. Theauxiliary heat supplied by member 21 anticipates the increasedtemperature that results'from the circuit being closed and the heateroperating upon a demand of heat in the room or space in which thethermostat is located.

A portion of leg 29 is cut away at 32. A bowed spring 33 having a doublereverse curve is secured at 34 and 35 to leg-29 to operate in thiscut-away portion 32. A movable contact designated generally as 36 ismounted upon bowed spring 33 and is adapted to make and break contactbetween two oppositely arranged relatively stationary contacts 31 and38. Brackets 39 and 40 carfy stationary contact 31 and 38 in opposed butadjustable relation as shown, and are secured upon raised face I 0 onopposite sides of projection I3.

that stationary contact 38 may be used, for example, as ahot contact orotherwise in the event the device is connected in a three-wire system.Brackets 39 and 48 are U-shaped and each is provided with outwardlyextending legs, one of which adjustably carries stationary contacts 31and 38, while the other of which receives opposed relatively fixed stopmembers 4| and 42. Stationary contacts 31 and 38 are preferably disposedin the same horizontal plane with fixed stop members 4| and 42. As shownmore specifically in Figs. 11 and 12, upper U-bracket 40 has one shortoutwardly extending leg 43 (Fig. 12) with a depending slotted ear 44 anda long outwardly extending leg 45 (Fig. 11) with a depending car 46 ofsubstantially the same length. Fixed stop member 42 is adjustablycarried in slotted ear 46 while relatively stationary contact 38 isadjustably carried in slotted ear 44. U-bracket 39 has similar legs 41and 48. Leg 41 has an upstanding slotted ear 49 that receives relativelystationary contact 31 and leg 48 has an upstanding slotted ear 58 thatcarries fixed stop member 4|. Leg 48 is longer than leg 41. As a matterof fact, leg 45 of bracket 48 and leg 48 of bracket 39 are of the samelength so that the fixed stop members 4| and 42 carried in slotted ears48 and 58 will be in alignment with each other. Leg 43 and leg 41 ofbrackets 48 and 39, respectively, are of the same length so that therelatively stationary contacts 31 and 38 will be in alignment with eachother. In this connection, stationary contact 31 is in electricalrelation with fixed stop member 4| because they are carried on the samebracket 39, leg 48 thereof receiving the upper end of the preheatingelement 21 at 52. Stationary contact 38 is in electrical relation withfixed stop member 42 because they are carried by bracket 48.

Leg 29 of the bimetallic element is adapted to operate between fixedstop members 4| and 42, and, as will be presently explained, this leg 29will break contact with either stop member before movable contact 36 onbowed spring 38 breaks contact with the stationary contact members 31and 38. Likewise, leg 29 will make contact with either stop member 4| or42 after movable contact 38 on bowed spring 38 makes contact with thestationary contact members 31 and 38, as willappear in the drawings (seeFigs. 13 to 17, inclusive). The reduced portion of this leg 29, formedas the result of cutting away a part to provide a space in which bowedspring 33 operates, will move between fixed stop members 4i and 42 whilebowed spring 33 with its movable contact 36 will operate between saidrelatively stationary contact members 31 and 38. Bowed spring 33 is astrip of resilient or spring material formed into a double reverse.curve as it is attached to leg 29 at 34 and 35 so that the stressapplied endwise will maintain the spring in the form of this doublereverse curve. The limited movement of movable contact 36 operatingbetween closely spaced stationary contact members 31 and 38 and thecompressive force or stress applied endwise to bowed spring 33 keep, itis believed, this bowed spring in a state of unstable equilibrium, theresulting tension holding movable contact 36 under pressure against thestationary contact member that the latter engages. For example, ifmovable contact 36 engages stationary contact member 31, leg 29 will bein a position toward or against the opposite fixed stop member 4| (seeFigs. 13 and 14). A change of temperature influencing bimetallic member23 to move its leg 29 to the left will increase the tension of bowedspring 33 until a condition is reached where the increasing bendingmoment applied thereto causes it to disengage movable contact 36 fromstationary contact member 31 with a snap action, this bowed springthereby moving in a direction opposite to the movement of leg 29. Theincreasing bending moment or stress imparted to spring 33 effectsmaximum contact pressure between movable contact 36 and stationarycontact member 31 at the time of the break. The switch operatessubstantially as an overcenter device but the spring 33 will remain inunstable equilibrium as movable contact 36 strikes and remains engagedagainst stationary contact member 38.

Stating the action of the bimetallic member 23 and the bowed spring 33differently, starting at any given point, the bimetallic member and thebowed spring are in a certain fixed position. Now, if the device issubjected to a temperature change tending to cause it to move toopposite position, storage of energy in the bowed spring 33 will beginas well as a. like amount of ener y in the bimetallic member 23, whichtends to drive the movable contact 36 carried by the bowed spring 33against the stationary contact which it is then engaging. When theenergy stored in the bimetallic member 23 becomes sufficient to overcomethe reaction of the bowed spring 33, the balance between the two isbroken, the bimetallic member 23 moves forwardly very rapidly and thebowed spring 33 simultaneously accelerates with extreme rapidity andmoves in the opposite direction of the bimetallic member.

In Figs. 8 and 9, both positions of bowed spring 33 are shown and themovable contact is designated generally as 38. Fig. 10 illustrates at anenlarged scale the construction of movable contact 36. Care must beexercised in shaping movable contact 36 to prevent a molecular change inspring member The contact is inserted through an aperture in bowedspring 33 and head 59 may be first formed. Care is then exercised toprevent striking the bowed sprin 33 as head is formed so as not tochange the original characteristics of the spring material.

Manually adjustable member 9 carrying pointer 8 that registers withcalibration markings 9' and rides in slot 7! in casing 2 is pivotallyconnected to base i at 55 by a screw that extends through the base andis held in position by nut 56 atthe rear side. An abutment 51 is carriedand operated by manually adjustable member 9 to engage upper end 58 ofbimetallic leg. 38 to modify the action of spring mounting 22 andthereby predetermine the temperature setting at which the bimetallicelement 23 will operate to make or break contact between movable contact36 and the stationary contact members 31 and 38. As previously stated,spring mounting 22 functions to support bimetallic element 23 infree-floating relation and urges the same clockwise to bring leg 29 intoengagement with the right-hand fixed stop 4i (see Fig. 13). As abutment51 is pressed against upper end 58 of leg 38 by a left-hand pivotalmovement of manually adjustable member 9 which raises abutment 51upwardly to bring it against this upper end 58 of leg 30 and slide ittherealong, bimetallic element 23 is tilted counterclockwise against theaction of spring mounting 22. Leg 29 will thereby be moved to the leftfrom engagement with right-hand fixed stop member 4| and the position itis given between fixed stop members 4| 7 and 42 will determine thetemperature setting of the device (see Fig. 14). Abutment 61 is securedto leg 59 of a right angular bracket including leg 69 that is adjustablyattached to manually adjustable member 9. Leg 60 is slotted as indicatedat 6| in Figs. 6 and 18, there being provided a struckup car 62 that,adjustably receives a screw 63 and has its end 64 bearing against theedge of manually adjustable member 9.

A bolt 65 is adapted to securely fasten leg 69 to manually adjustablemember 9 (see Fig. 18.) Any suitable construction for securing thisattachment may be provided. As shown, however, a boss 66 on manuallyadjustable member 9 is adapted to ride in slot 6| in leg 60, the partsbeing held together by bolt 65 threadedly engaging the disk 61 at therear. Bolt 65 freely passes through a front washer 66 with its headrecessed so as to lie flush with the face of washer 69. Loosening bolt65 permits relative movement so as to move bracket 60 laterally withrespect to manually adjustable member 9. This adjusts the position ofthe abutment 61 with respect to its engagement with leg 39 of thebimetallic element 23. The construction described furnishes means foreffecting proper calibration of the thermostat that is simply and easilymade. After bolt 66 has been loosened to allow movement between leg 60and manually adjustable member 9, screw 63 may be adjusted to move leg69 to the right or to the left so as to increase or decrease thepressure exerted by abutment 51 against leg 30. An original calibrationmay be made in this manner by the adjustment described so that the leg29 will be in a position with respect to fixed stop members 4| and 42 tomove in either direction to make or break contact between movablecontact 36 and stationary contact members 31 and 38 at a giventemperature. For example, a calibration may bemade which will causeoperation of the bimetallic member 23 at a given temperature. After thiscalibration is made, operation of the manually adjustable member will somodify the action of spring mounting 22 upon bimetallic element 23 as toadjust the position of leg 29 between fixed stops 4| and 42 as to causeoperation at any desired temperature. If an original calibration is madethrough the means above described at a given temperature, say, 70 F.,with the pointer 8 registering with the corresponding calibrationmarking, as shown in Fig. 2a, the relation between abutment 61 and leg39 is such that upon further movement or adjustment of manuallyadjustable member 9 to another temperature setting, the bimetallicelement 23 will be in an adjusted position to operate at this newtemperature setting to either make or break the contact.

Fig. 13 is a detail view specifically illustrating the position of bothbimetallic legs 29 and 39 and the movable contact 36 when manuallyadjustable member has been swung to the right to bring abutment 51 outof engagement with leg 39. The action of spring mounting 22 uponbimetallic element 23 to swing its both legs to the right or f clockwisewill be noted in this Fig. 13. Leg 29 is brought to bear against fixedstop 4| thereby exerting a bending moment upon bowed spring 33 to holdmovable contact 36 against stationary contact member 31. The circuitwill then be closed.

Fig. 14 illustrates a position of the various parts after manuallyadjustable member has been swung to the left to bring abutment 51against leg 30 so as to modify the action of spring mounting 22 upon thelegs of bimetallic element 23; This position may represent the positionof the bimetallic element after a proper calibration has been madethrough adjusting screw 63 and its associated parts to cause operationof the bimetallie element at a predetermined temperature to actuate thebowed spring 33 for breaking circuit between movable contact 36 andstationary contact member 31. It will be noted that leg 29 has beenmoved to the left and out of engagement with fixed stop 4|.

Fig. 15 represents the position of the various parts after atemperature'change representing the predetermined setting previouslygiven through the manually adjustable member 9. It will be noted thatleg 29 has been moved farther to the left and has caused bowed spring 33to effect disengagement of movable contact 36 from stationary contactmember 31 by a snap action. This will result in movable contact 36engaging stationary contact member 33. As stated, leg 29 has moved tothe left. For the adjustment given and the change effected, asillustrated in Fig. 15, this leg 29 has not moved sufficiently to engagefixed stop 42. As the device is calibrated and constructed to operate,the positioning of manually adjustable member 9 to the left providespredetermined temperatureisettings at lower temperatures. If thethermostat herein disclosed is employed in a three-wire system, say forexample only, where stationary contact member 31 represents a coldcontact operable when engaged by movable contact 36 to close a heatingcircuit during winter operation, the stationary contact member 38 mayrepresent the hot contact in the system for summer operation and may beused to close a circuit upon a rise of temperature instead of openingthe circuit, as in the case of stationary contact 31. It will beunderstood that this illustration is given as one example of thepossible adaptation of the thermostat herein disclosed. Fig. 16 thenrepresents the position of the parts when leg 29 engages fixed stopmember 42, while Fig. 17 represents the position of the puts after thepredetermined temperature setting effecting operation of the thermostatat higher temperatures as may :be necessary in summer operation. I

Figs. 13 and 14 illustrate that leg 29 will disengage fixed stop 4|before movable contact 36 disengages stationary contact member 31 whileFigs. 16 and 1'! illustrate that leg 29 will disengage fixed stop 42before movable contact 36 disengages stationary contact member 33. Thecircuit is always broken by the snap action provided by bowed spring 33,and therefore, the slow make and break between leg 29 and fixed stops 4|and 42 are ineffectual to cause any sparking.

Thermostats are usually mounted on walls and are, therefore, apt to beinfluenced by the temperature of the wall rather than by the temperatureof the surrounding air. Efllcient operation of the thermostat will onlybe obtained if the arrangement prevents or minimizes wall temperatureinfluence upon the thermostatic eleslots and enter or otherwise arefastened to the wall, as indicated at I5. Vertical adjustment of wallplate I may be first obtained by means of vertical slot I4. The topscrew may then be inserted through slot 14 and fastened in wall I5.Horizontal alignment to secure a true vertical position for the wallplate may be obtained by means of horizontal slot I3 before the screw issecurely fastened. Spring fingers I6 and "are slotted, as illustrated,and fastened at 18 by rivets, or the like, to wall plate Ill. The upperend of these spring fingers I6 and 11 are curved outwardly to be spacedfrom the wall plate whereby through the means of slots I9 the thermostatmay be attached to wall plate 10 by bringing headed studs 80 on base Iinto engagement with the slotted springs 16 and TI. The reduced shank ofheaded studs 80 may ride in slot I9 while the heads will lie betweenspring fingers and the wall plate, but preferably without the headstouching the wall plate, thereby securely holding the thermostat againstthe wall and upon mounting plate 10, as shown in Figs. 3 and 19. Wallplate I0 may be made of metal. In order to reduce conduction of heatbetween wall plate I0 and the thermostat, spacing lugs 8| are struckupat suitable points, say, at the corners of the central opening 82. Thesespacing lugs are of relatively small width, being somewhat V-shape andpractically provide point contacts only with base I, as illustrated at83. Spacing lugs BI, therefore, hold base I away from wall plate 10 andprovide an enclosed air space to act as insulation, it being noted thatperipheral flange I2 of base i encloses this space and is brought intocontact with the wall. Base I and therefore flange I? is made ofcomposition insulation material that is a low conductor of heat, andconsequently, engagement of wall 85 by flange I2 will not ma- 40terially affect the action of the thermostatic element 23 by anyconduction of heat that may take place between this flange I2 and themounting wall. Central opening 82 further advantageously permits readyconnection of the circuit wires to 45 such terminals as I6, I! and I8 atthe back of base I. It will be apparent that wall plate ID has numerousadvantages and features in connection with mounting and holding thethermostat against a wall surface. The thermostat may be 50 removed atany time from against the wall without removing the wall fasteningbolts, which, if removed a number of times might enlarge their openingsin the wall and be loose therein. Moreover, the thermostat will not beinfluenced by a 55 cold wall which often occurs and causes operation ofthe thermostatic member independently of any demand for heat that may benecessitated by air temperature in the room. It will further be observedthat a space 86 might be provided be-= 60 tween the edges of plate I0and the peripheral flange I2 of base I, and that the fit of the heads ofstuds 80 in slotted spring fingers I6 and Ti will not bring these headsin contact with plate It! (see Figs. 3 and 19). Hence, an arrangementmay be obtained whereby the only contact between wall plate III and baseI of the thermostat of bimetallic element 23 is preferably of greaterexpansion than inner member 9|. We find that such construction of abimetallic member prevents any permanent rupturing of the parts by thelegs opening too far when the device is shipped unprotected into coldclimates in winter.

From the foregoing description it will be observed that an improvedthermostatic structure has been described that is exceedingly sensitiveto temperature change but yet sturdy in construe I character thatnecessarily provides accuracy of calibration at the time factoryadjustments are made. This calibration is made at the room temperatureat the time manually adjustable member 9 is moved to bring pointer 8 tothe corresponding calibration marking 9'. Screw 65 is slightly loosenedand screw 63 is then operated to move manually adjustable member 9 andconsequently leg 29 until movable contact 36 breaks contact withrelatively stationary contact member 31. Screw 65 is again tightened andthe de= vice is ready for use. Thus, the adjustment is very simple. Inorder for the thermostat to operate thereafter at differenttemperatures, manually adjustable member 9 is moved to bring pointer 8to the corresponding calibration marking 9.

The thermo responsive element is preferably in the form of a bimetallicmember substantially of U-shape supported by a spring mounting thattends to press the legs together after one of the legs has been broughtto bear against a fixed stop member. This said one leg is preferablyprovided with a bowed spring held under tension so as to be kept inunstable equilibrium whereby when this said one leg of the bimetallicmember moves, the tension of the bowed spring increases and continues toincrease until it snaps to another position whereby to break the circuitby a movable contact carried thereon. This arrangement of the bimetallicelement and its spring support admits, therefore, of the adoption of aunique and efficient form of calibrating means that is simple and easyto operate, as explained above.

It will be kept in mind that one of the primary purposes of the presentinvention is to provide a practical, efiicient and exceptionallysensitive thermostat of the character described, which, in

view of its accomplishments, is relatively inexpensive to manufacture.

' Without further elaboration, the foregoing will so fully explain thegist of our invention that others may, by applying current knowledge,readily adopt the same for use under varying conditions of service,without eliminating certain features, which may properly be said toconstitute the essential items of novelty involved, which items areintended to be defined and secured to as by the following claims.

We claim: 1. A thermostat comprising a substantially U shaped bimetallicelement having a movable contact on one of its legs, a relativelystationary contact on each side of said movable contact, a springmounting for said bimetallic element to provide a free floating movementthereto, said mounting being secured to the opposite leg of saidbimetallic element and tending to urge said legs together, and a memberengaging said opposite leg for modifying the action of said mounting onsaid legs whereby to predetermine the operatng temperature of saidbimetallic element to actuate said movable contact.

2. A thermostat comprising a substantially U- shaped bimetallic elementhaving a movable contact on one of its legs, a relatively stationarycontact on each side of said movable contact, a spring 5 mounting forsaid bimetallic element to provide a free floating movement thereto,said mounting being secured to the opposite leg of said bimetallicelement and tending to urge said legs together, and a manuallyadjustable member for modifying the action of said mounting on said legsto predetermine the operating temperature of said bimetallic element toactuate said movable contact.

3. A thermostat comprising a substantially U- shaped bimetallic elementhaving a movable contact on one of its legs, a relatively stationarycontact on each side of said movable contact, a mounting for saidbimetallic element tending to urge the legs thereof together, and meansfor modifying the action of said mounting on said legs to predeterminethe operating temperature of said bimetallic element to actuate saidmovable contact, said means engaging the opposite leg of said bimetallicelement beyond the point of connection of said mounting.

4. A thermostat comprising a substantially U- shaped bimetallic elementhaving a movable contact on one of its legs, a relatively stationarymember on each side of said movable contact, at least one of saidstationary members constituting a contact cooperating with said movablecontact, a resilient mounting for said bimetallic element tending tourge its legs together, means for modifying the action of said mountingon said legs to predetermine the operating position of said contact legsbetween said stationary members, and calibrating means operable tocalibrate the action of said modifying means to secure predeterminedtemperature settings of said bimetallic element through the operation ofsaid modifying means.

5. A thermostat comprising a substantially U- shaped bimetallic elementhaving a movable con-- tact on one of its legs, a relatively stationarymember on each side of said contact, at least one of said stationarymembers constituting a contact cooperating with said contact on saidbimetallic leg, a resilient mounting for said bimetallic element tendingto urge its legs together, and means for modifying the action of saidmounting on said legs to predetermine the operating position of saidcontact leg between said stationary members, said means comprising apivotally mounted manually operable member and a bracket adjustablycarried thereby for hearing against one leg of said bimetallic element.

6. A thermostat comprising a substantially U- shaped bimetallic element,a relatively fixed stop member on each side of one leg of saidbimetallic element, a spring mounting for said bimetallic element urgingsaid leg against one of said rela- 6o tively fixed stop members, meansfor engaging the opposite leg to oppose the action of said springmounting whereby to adjustably shift said one leg to any predeterminedposition between said relatively fixed stop members, and calibrat- 5 ingmeans for said engaging means for predetermining a temperature settingat which said bimetallic element will operate to move said one leg.

7. A thermostat comprising a substantially U- shaped bimetallic element,a bowed spring carried by one leg of said element, a movable contact onsaid bowed spring, a relatively stationary member on each side of saidmovable contact, at least one of said stationary members consti- 75tuting a contact cooperating with said 1 0mm? contact on said bowedspring, a relatively fixed stop member on each side of said leg, aspring mounting for said bimetallic element urging said leg against oneof said fixed stop members whereby said movable contact will be pressedagainst said stationary contact member, and means for engaging theopposite leg to oppose the action of said spring mounting whereby t0predetermine the operating temperature of said bimetallic element tosnap said bowed spring from one side to the other and break engagementof said movable contact with said stationary contact.

8. A thermostat switch for controlling an electric circuit comprising asubstantially U-shaped bimetallic element having a movable contact onone of its legs, a bowed spring carried by said leg on which saidmovable contact is mounted, a relatively stationary contact on each sideof said movable contact for causing said bowed spring to snap from oneside to the other to effect a quick make and break of the circuit assaid bimetallic element moves, a spring mounting for said bimetallicelement to provide a free floating movement thereto, said mounting beingsecured to the opposite leg of said bimetallic element, and anadjustable member tending to spread said legs and provide thereby anadjustable thermostatic setting of said contact carrying leg withrespect to said stationary contacts.

9. A quick acting thermostat comprising oppositelydlsposed relativelyfixed stop members and oppositely disposed relatively stationary contactmembers, a thermostatic member operating between said stop members, abowed spring carried by said thermostatic member, a movable contact onsaid bowed spring for engaging said stationary contact members, andmeans for urging said thermostatic member in either direction betweensaid stop members whereby to increase the tension of said bowed springand to secure thereby maximum contact pressure at the time said bowedspring snaps from one side to the other, said bowed spring movingoppositely in direction to said thermostatic member.

10. A quick acting thermostat comprising oppositely disposed relativelyfixed stop members and oppositely disposed relatively stationary contactmembers, a substantially U-shaped blmetallic member having one of itslegs operating between said stop members, a bowed spring carried by saidbimetallic member and operating between said stationary contact members,a movable contact on said bowed spring for alternately engaging saidstationary contact members, a mounting for said bimetallic member urgingsaid operating leg against one of said stop members, and an adjustablemember tending to modify said action of said mounting whereby to movesaid leg in the opposite direction, the movement of said leg in eitherdirection increasing the tension of said bowed spring to secure maximumcontact pressure at the time said bowed spring snaps from one sfde tothe other, said bowed spring moving oppositely in direction to saidbimetallic member.

11. A wall plate for mounting a thermostat comprising a substantiallyflat plate having a central cut-away portion, spacing lugs formed alongthe edges of said cut-away portion, and bifurcated fastening fingersadapted to receive fastening elements on the thermostat in slidabierelation.

. 2. A thermostat comprising a bimetallic element having a contactmovable therewith, a stationary contact, a resilient mounting for saidbimetallic element tending to hold said movable contact against saidstationary contact, and means for modifying the action of said mountingtending to hold said movable contact against said stationary contactwhereby to predetermine the operating temperature of said bimetallicelement that will actuate said movable contact.

13. A quick acting thermostat comprising a thermostatic member having acontact movable therewith, a stationary contact, a mounting for saidthermostatic member tending to hold said movable contact against saidstationary contact, a fixed stop against which said thermostatic memberabuts when'said movable contact engages said stationary contact, meansfor carrying said movable contact upon said thermostatic member toincrease the contact pressure between said movable contact and saidstationary contact as said thermostatic member is influenced by atemperature change to move away from said fixed stop, and means formodifying the action of said mounting tending to hold said movablecontact and said thermostatic member against said stationary contact andsaid fixed stop whereby to predetermine the operating temperature ofsaid thermostatic member to break contact between said movable contactand said stationary contact.

14. A quick acting thermostat comprising a thermostatic member, amounting for said thermostatic member to provide a free floatin movementthereto, a bowed spring carried by said thermostatic member, astationary contact, a contact on said bowed spring movable relative tosaid stationary contact, said mounting normally holding said bowedspring under compression with said movable contact engaging saidstationary contact, the formation of said bowed spring increasing thecompression tension thereof as said thermostatic member is influenced bya temperature change, and means for modifying the action of saidmounting whereby to predetermine the operating temperature of saidthermostatic element for breaking contact between said movable contactand said stationary contact.

15. A thermostat comprising a substantially U-shaped bimetallic element,a contact movable with one of the legs of said bimetallic element, arelatively stationary member on each side of said movable contact, atleast one of said stationary members constituting a contact cooperatingwith said movable contact, a mounting for said bimetallic element urgingboth legs thereof in a given direction until said movable contactengages one of said stationary members and thereafter tending to urgeboth legs together, and means for modifying the action of said mountingon said legs to predetermine the operating temperature of saidbimetallic element to actuate said movable contact.

16. A thermostat comprising a substantially U-shaped bimetallic element,a contact movable with one of the legs of said bimetallic element, arelatively stationary member on each side of said movable contact, atleast one of said stationary members constituting a contact cooperatingwith said movable contact, a mounting for said bimetallic element urgingboth legs thereof in a given direction until said movable contactengages one of said stationary members and there after tending to urgeboth legs together, means dition responsive mechanism on said base, awall plate, and means for detachably ,securing said base to said wallplate by a sliding movement of said base over and upon said wall plate,said means comprising projecting studs on the rear face of said base andbifurcated members on said wall plate for receiving said projectingstuds.

18. A wall mounting for a condition responsive device comprising, incombination, a base, condition responsive mechanism on said base, arearwardly extending peripheral flange on said base adapted to restagainst a wall on which said condition responsive device is to bemounted, a wall plate, a portion of said wall plate being cutaway toallow the passage of connections from said wall to the rear of saidbase, means for fixedly securing said wall plate in a predeterminedposition on said wall, means on said base for receiving said connectionsat the rear thereof, and means for detachably securing said base to saidwall plate by a sliding movement of said base over and upon said wallplate after said connections have been attached to the rear of saidbase, said wall plate being enclosed by said peripheral flange.

19. A thermostat comprising a base, a temperature responsive elementmovable parallel to said base, a bracket on said base extendingperpendicularly therefrom, a substantially flat resilient bar bent atboth ends for attachment to said bracket and said temperature responsiveelement, said bar providing a free floating resilient mounting for saidtemperature responsive element, the connection of said bar at saidbracket including a fastening member carried by said bracket and a slotin said bar for receiving said fastening member in adjustable relation.

20. A thermostat comprising a base, a bimetallic strip bent intermediateits ends to form an elongated U-shaped member disposed upon said base,means for mounting said bimetallic strip including a bracket secured tosaid base and having an arm extending perpendicularly therefrom, aresiliently formed bar having one end secured to one leg of saidbimetallic strip and the other end slotted for connection to saidbracket arm in adjustable relation, and a manually operable memberhaving a surface movable against said leg of said bimetallic strip tomodify the resilient action of said mounting bar.

21. A thermostat comprising a base, a substantially U-shaped bimetallicelement, mounting means for said bimetallic element, said mounting meansconnecting one leg to said base to provide a free floating movement tosaid bimetallic element and cause ambient temperature changes to affectthe position of the opposite leg, said opposite leg having a portionthereof cut away, a bowed spring suspended across said outa-way portionand secured to said leg to move therewith, a contact on and movable withsaid bowed spring, stationary contacts on opposite sides of said springcontact, said movable contact operating to swing with said bowed springto opposite sides of said leg through its said cuta-way portion toeffect a sensitive quick make and break with said stationary contacts.

22. A thermostat comprising a bimetallic element having a contactmovable thereby, means for tiltably mounting said bimetallic element,and adjusting and calibrating means for predetermining the operatingtemperature of said bimetallic element to operate said movable contactcomprising a swinging lever and an abutment mounted thereon for engagingand modifying the tiltable position of said bimetallic element, themounting of said abutment including a member normally locked to saidswinging lever and means for moving said member relative to saidswinging lever when in an unlocked condition whereby to adjust thepressure of said abutment against said bimetallic element.

- 23. A thermostat comprising a bimetallic ele ing member carried bysaid bracket and engaging said lever toadjust the position of saidbracket relative to said lever.

24. A thermostat comprising a bimetallic element having a contactmovablethereby, means for mounting said bimetallic element so that a tiltingmovement about said mounting means when said bimetallic element isinfluenced by temperature changes will operatesaid movable contact, andcalibrating means for predetermining the operating temperature of saidbimetallic element to actuate said movable contact comprising a swinginglever;'a bracket movably carried on said lever, means movable by saidbracket for engaging said bimetallic element, and a calibrating membercarried by said bracket and engaging said lever to adjust the positionof said bracket relative to said lever, and means for normally lockingsaid bracket against the action of said calibrating member.

25. A quick acting thermostat comprising oppositely disposed relativelystationary members, at least one of which is a contact member, athermostatic element having a contact movable thereby for operatingbetween said stationary members, a bowed spring under tension mountedupon said thermostatic element to carry said movable contact, oppositelydisposed relatively fixed stops for limiting the movement of saidthermostatic element, both said fixed stops and said stationary membersbeing spaced a distance apart from each other respectively to hold'saidbowed spring in unstable equilibrium when said movable contact isagainst either one of, said stationary members, and means for normallyurging said thermostatic member against one of said fixed stops wherebymovement of said thermostatic member away from the said fixed stop by atemperature change will increase the energy stored in said bowed springto secure maximum contact pressure at the moment of breaking enzagementof said movable contact.

JOHN S. BAKER. ROY M. SCHULTZ.

CERTIFICATE OF CORRECTION.

Patent No. 2,222, 062. November 19, 19140.

" JOHN s. BAKER, ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 5,second column, line 62, for the word "as" read --us--; page 7, firstcolumn, line 14.1, claim 11+, strike out "tension"; and that the saidLetters Patent should-be read with this correction therefn that the samemay conform to the recorder the casein the Patent Office. I Signed" andsealed this 114th day of January, A. D. 19in.

Henry Van Arsdale, (S681) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION. Patent No. 2,222, 062. November 19, 1911p.-

" JOHN "s. BAKER, ET AL.

It is hereby certified that error appears in the printed specifieationof the sbove numbered patent requiring correction as follows: Page 5,sec:-

end colum1i, line 62, for the word "as" read ---us; page 7, firstcolumn, line 14.1, claim 11]., strike out "tension"; and that the saidLetters Patent should-be resd vith this correction thereih that theseine may conform to the recorder the case in the Patent Office.

Signed and sealed this day of January, A. D. l9hl.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

